There are two kinds of radiation therapy; one is the internal radiation therapy that radioactive material is administered into the lesion to emit radiation in the human body, and the other is the external radiation therapy that radiation is emitted from the outside of the body through special equipments.
In the internal radiation therapy, radioactive materials are administered orally, intravenously or by injecting directly into the body. But the internal radiation therapy has not yet been utilized widely on the reason that a radioactive material administered to the lesion may be leaked out and spread to the whole body through blood flow, and accumulated to other organs or tissues, and it results in a fatal damage to other organs, especially bone marrow very sensitive to radiation. Therefore, most malignant tumors have been treated by the external radiation therapy.
The external radiation also has many problems. For the external radiation therapy, radionuclides with high penetrative radiation should be used, since the rays are emitted out of the body, and it results in the irradiation of adjacent normal tissue as well as the lesion. And it is not convenient to use the external radiation on account of expensive equipments, hospitalization and the like.
The inventors have conducted intensive research in order to find the way of irradiating the lesion conveniently and invented the new therapeutic type for irradiation to patients. That is, radioactive material is prepared in a form of patch/film which makes irradiation easy and irradiates lesion site specifically.